H. influenzae type b is an important cause of disease, particularly in infants and small children who fail to produce antibodies following active immunization. See J. C. Parke, Jr. et al, J. Pediatr., 81:765 (1972); J. Ward et al, N. Eng. J. Med., 301:122 (1979); and H. Petola et al, Pediatrics, 60:730 (1977). The rapid diagnosis of H. influenzae type b disease is important for the selection and timely administration of antibiotics. The H. influenzae type b bacterium is particularly characterized by a polyribosylribitol phosphate (PRP) capsular polysaccharide. Another pathogenic microorganism bearing PRP capsular polysaccharide is E. coli having the K100 antigen. This pathogen is known to produce septicemia, pneumonia and meningitis in humans. Other pathogens bearing PRP capsular polysaccharide may yet be identified. The pathogenicity of the two known PRP-bearing microorganisms is believed to be limited primarily to humans.
Currently, polyclonal anti-PRP antibodies raised in animals such as rabbits are employed in various assays to identify the PRP antigen. However, such polyclonal reagents often have more than one specificity and therefore tend to produce unwanted cross reactions. PRP isolated from H. influenzae type b bacterium has also been used to prepare a combined vaccine, as exemplified in U.S. Pat. No. 4,220,717 to Kuo. Also known is an assay for the detection of PRP capsular polysaccharide, as exemplified by U.S. Pat. No. 4,310,508 to Siber.
The technique of fusing cells to produce viable hybrids that express characteristics of both parental cells has been known for a number of years. In Nature, 256:495 (1975), Kohler and Milstein reported the successful fusion of mouse B lymphocytes and mouse plasmacytoma cells to form hybrids that secreted monoclonal antibodies of predefined specificity. In Proc. Nat'l. Acad. Sci., USA, 77:5429 (1980), Olsson and Kaplan documented the first human-human hybridomas that secreted human monoclonal antibodies. In order to avoid the cross reactions of polyclonal anti-PRP antibodies, to provide a very precise antibody for the rapid diagnosis of disease caused by a PRP-bearing pathogen, and to provide an endless supply of antibody that can be generated in vitro, there is needed a self-reproducing carrier cell containing genes that produce a human monoclonal anti-PRP antibody and a method for producing the antibody from the carrier cell. Such an antibody would be, to our knowledge, the first human monoclonal antibody reactive with a major human pathogen. Advantageously, this antibody could be produced by in vitro culturing of the carrier cell, thereby avoiding injection of the antigen into an animal and later killing the animal.
As a result of the inability to vaccinate certain high risk groups such as infants and immunosuppressed adults, there is also a need for a means of passive prophylaxis against disease caused by a PRP-bearing pathogen, using a human monoclonal antibody. Additionally, a human monoclonal antibody that is therapeutically effective against an existing disease caused by a PRP-bearing pathogen would be of substantial value. Such an antibody would be, to our knowledge, the first human monoclonal antibody to demonstrate a functional activity against a pathogenic organism.
Moreover, there is a need for a laboratory reagent for dissecting the chemical structure of PRP capsular polysaccharide.